I have my 90 gallon tank running for about 2 weeks now. I let it cycle instantly by rinsing my dirty filter on my old tank. The plants been there about 4 days. I left out of town last weekend and i have to turn my lights and co2 off coz i dont want any problems happening when Im out. When I can back i saw alot of surface scum buildup. This tank has a build-in overflow and dont know why is still have a surface scum on top. I dont have my discus fish there yet coz i still want to make sure that this tank is running smoothly. This tank has a big driftwood that still wants to float but its tied down at the bottom. I will take pictures of it soon. Pls help.